Recently did some repairs on a system that someone else installed. The orion 12/12-30 isolated was not charging the house batteries, it was not even showing up on bluetooth. They ran from the starter battery with 4 gauge wire but put a MIDI fuse holder with 8 gauge wire and a 40 amp fuse at the starter battery terminal. The fuse holder melted and it appeared the fuse blew. I was swapping in a 60 amp circuit breaker to restore power and correct the install. I then noticed the midi fuse never actually blew.
I then tested the positive wire to ground and there I got a reverse polarity reading, only around -10 volts. The starter battery was disconnected. I then killed the house battery main disconnect and still read -10 volts at the positive wire of the orion input. I disconnected every fuse at the house bus bar, with the same result.
At this point my best guess was that the solar was somehow powering up the system, although we were parked indoors with only led lights on the panels.
Is it normal for the Orion to read as a reverse polarity when connecting test probes to the input wires? Or was this an anomaly caused by other installation issues? Once the system was reconnected, everything worked correctly again.
